libsys: various updates

- move system calls for use by services from libminlib into libsys;
- move srv_fork(2) and srv_kill(2) from RS and into libsys;
- replace getprocnr(2) with sef_self(3);
- rename previous getnprocnr(2) to getprocnr(2);
- clean up getepinfo(2);
- change all libsys calls that used _syscall to use _taskcall, so as
  to avoid going through errno to pass errors; this is already how
  most calls work anyway, and many of the calls previously using
  _syscall were already assumed to return the actual error;
- initialize request messages to zero, for future compatibility
  (note that this does not include PCI calls, which are in need of a
  much bigger overhaul, nor kernel calls);
- clean up more of dead DS code as a side effect.

Change-Id: I8788f54c68598fcf58e23486e270c2d749780ebb

lib/libsys/sef.c

@@ -9,7 +9,7 @@
 /* Self variables. */
 #define SEF_SELF_NAME_MAXLEN 20
 char sef_self_name[SEF_SELF_NAME_MAXLEN];
-endpoint_t sef_self_endpoint;
+endpoint_t sef_self_endpoint = NONE;
 int sef_self_priv_flags;
 int sef_self_first_receive_done;
 int sef_self_receiving;
@@ -68,8 +68,8 @@ void sef_startup()
   if((sef_self_priv_flags & ROOT_SYS_PROC) && sef_self_endpoint != RS_PROC_NR) {
       r = vm_update(RS_PROC_NR, sef_self_endpoint);
       if(r != OK) {
-          panic("unable to update RS from instance %d to %d",
-              RS_PROC_NR, sef_self_endpoint);
+          panic("unable to update RS from instance %d to %d: %d",
+              RS_PROC_NR, sef_self_endpoint, r);
       }
       old_endpoint = sef_self_endpoint;
       sef_self_endpoint = RS_PROC_NR;
@@ -190,6 +190,19 @@ int sef_receive_status(endpoint_t src, message *m_ptr, int *status_ptr)
   return r;
 }
 
+/*===========================================================================*
+ *				sef_self				     *
+ *===========================================================================*/
+endpoint_t sef_self(void)
+{
+/* Return the process's own endpoint number. */
+
+  if (sef_self_endpoint == NONE)
+	panic("sef_self called before initialization");
+
+  return sef_self_endpoint;
+}
+
 /*===========================================================================*
  *				sef_cancel				     *
  *===========================================================================*/